dm round robin: do not use this_cpu_ptr() without having preemption disabled

Use local_irq_save() to disable preemption before calling
this_cpu_ptr().

Reported-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Fixes: b0b477c7e0dd ("dm round robin: use percpu 'repeat_count' and 'current_path'")
Cc: stable@vger.kernel.org # 4.6+
Suggested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-round-robin.c b/drivers/md/dm-round-robin.c
index 4ace1da17db8f4473fcb72d546a1067b943bc87b..6c25213ab38c8d271ff58e093adee523571443ed 100644 (file)
--- a/drivers/md/dm-round-robin.c
+++ b/drivers/md/dm-round-robin.c
@@ -210,14 +210,17 @@ static struct dm_path *rr_select_path(struct path_selector *ps, size_t nr_bytes)
        struct path_info *pi = NULL;
        struct dm_path *current_path = NULL;
 
+       local_irq_save(flags);
        current_path = *this_cpu_ptr(s->current_path);
        if (current_path) {
                percpu_counter_dec(&s->repeat_count);
-               if (percpu_counter_read_positive(&s->repeat_count) > 0)
+               if (percpu_counter_read_positive(&s->repeat_count) > 0) {
+                       local_irq_restore(flags);
                        return current_path;
+               }
        }
 
-       spin_lock_irqsave(&s->lock, flags);
+       spin_lock(&s->lock);
        if (!list_empty(&s->valid_paths)) {
                pi = list_entry(s->valid_paths.next, struct path_info, list);
                list_move_tail(&pi->list, &s->valid_paths);